Lunar eclipses

What is the Blue Supermoon Lunar Eclipse?

Cut through the sensationalism and get the facts on what you’ll see on January 31

A Blue Supermoon Lunar Eclipse is coming. It’s a dream scenario for sensationalist websites, who are increasingly one-upping each other on how absolutely amazing they can frame an upcoming night sky event. So a Blue Supermoon Lunar Eclipse is a bit of a dream come true for the internet.

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Where can I see the Blue Supermoon Lunar Eclipse from?

For those in the western half of the US and Canada, the event will be viewable in the early hours of January 31. For those Australia and Asia, it will be early evening.

What does it all mean?

Let’s take the phrase ‘Blue Supermoon Lunar Eclipse’ and break it down, with a focus on what stargazers and moon-watchers will see on January 31.

– Blue Moon

What is a Blue Moon? Nothing more than the occurrence of two Full Moons in one calendar month. The Moon takes 27.32 days to go round Earth, so sometimes (and actually quite often – also in March 2018!), there are two inside one month.

What will I see? Nothing – it won’t be blue. It’s just a calendar quirk.

– Super Moon

What is a Super Moon? The moon’s orbit around Earth is elliptical, so sometimes it’s closer. When that coincides with a Full Moon, it’s called a supermoon. They often come in twos or threes because of tiny changes in the Earth’s orbit of the Sun. There was a supermoon on both December 3, 2017 and on January 1, 2018.

What will I see? The moon will look slightly bigger than normal, but only by a few percent. It’s a spectacle that’s completely overblown by the internet, and actually very hard to notice. It’s best seen by watching the Full Moon rise; it’s really only then that the Moon will appear bigger than usual.

– Total Lunar Eclipse

What is a Total Lunar Eclipse? Also called an umbral eclipse because the whole of the Moon fully enters the darkest part of Earth’s shadow, a total lunar eclipse starts with a penumbral, then a partial lunar eclipse, losing all of its usual Full Moon brightness. As it begins to enter the dark umbral shadow of Earth, one edge begins to look a little orange, though not until the dark shadow has spread right across the lunar surface will it look completely colored. This is totality, where Sun-light is being bent through the Earth’s atmosphere and on to the Moon. After as much as an hour of totality (depending on how far into the umbra the Moon is passing) the process then reverses, with the color quickly receding as the Moon exits the Earth’s umbra.

What will I see? At first you’ll see the Full Moon’s brightness dim hugely, then as it enters Totality it will turn deep pink, copper or orange – and possibly even red (if there has been significant volcanic activity and the atmosphere is full of ash). Hence the name ‘blood moon’.

Image credit: CC0 Creative Commons